In optical character recognition systems video image information is reduced to a black/white decision from multi level gray information before character recognition can be accomplished. The performance of any character recognition technique is dependent upon the quality of the video information being processed. The technique for reducing mutli level image information to black/white decisions determines the quality of the video image. One such technique for the data reduction to black/white images is referred to as correlation. Correlation is achieved by taking digitized and quantized output values for each cell in a scanning matrix to generate a black or white data signal for each cell. The values of the cells surrounding the data point cell are summed and added to the value of the data point cell. Such a correlation technique is found in U.S. Pat. No. 3,761,876. In that patent, the value of the data point cell is multiplied by the number of cell values summed and compared with the cell value sum. A relative black signal is generated if the cell value sum is greater. Problems occur however, when the background from which a character is to be read is improperly established. Improper referencing of the background may be due to reflectance variations caused by multi colored backgrounds, paper textures, and other markings independent of that which is to be read, which result from ink smears or over printing on documents such as checks due to cancellations or endorsements. It is apparent then that it is necessary to be able to take into account such interfering backgrounds which tend to prevent the system from accurately reading the information printed thereon.